We have developed InGaAs linear arrays for Earth remote sensing for a long time. Results from spaceborne detectors have shown unexpected radiation damage: the dark current of some pixels, scattered over the array, increases in a stepwise manner, and the affected pixels randomly oscillate between metastable states. Ground irradiation tests with high energy protons have provided evidence that the damage is located in the InGaAs diodes, and is enhanced by the CCD readout mode, which requires a approximately -1V reverse bias. A detailed analysis of the mechanisms involved is presented, and led to the design of a new readout circuit based on CTIA amplifiers which integrate the photocurrent around zero bias. This new readout mode is much less sensitive to dark current drifts and instabilities, as the dark current is reduced by several orders of magnitude compared to the previous design. Furthermore, the noise level is improved by 30 percent. Besides this basic improvement, the pixel pitch was halved to increase the ground resolution, so that the new array contains 6000 pixels. The performance is described with a particular focus on noise properties. This new array was tested under proton irradiation with negligible effects.
InGaAs SWIR imaging detectors hardening against proton irradiation
2003
10 Seiten, 4 Quellen
Conference paper
English
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